It is generally known to vary fuel injection timing, which is the time a given fuel injection quantity is delivered to an engine, as a function of engine temperature, such as may be indicated by engine coolant temperature. Furthermore, it is generally known to vary the fuel injection quantity itself as a function of variations in atmospheric pressure, generally to compensate for variations in air density that may lead to variations in engine air/fuel ratio. Such conventional engine control fails to compensate for changes in homogeneity of the air/fuel mixture caused by varying barometric pressure. For example, engine air intake manifold absolute pressure decreases with decreasing barometric pressure, leading to a reduction in air/fuel mixing before combustion. The reduction in air/fuel mixing leads to a less uniform air/fuel mixture available for combustion which can lead to incomplete combustion. Incomplete combustion leads to decreased engine performance and increased hydrocarbon HC levels in engine exhaust. Increased HC levels can lead to decreased catalytic converter efficiency and increased converter temperatures which can reduce converter durability. Such difficulties are not resolved through conventional approaches to fuel injection control.
It would therefore be desirable to compensate for changes in barometric pressure, such as caused by changes in the altitude at which a vehicle including a catalytic treatment device is operated, so as to provide for more uniform air-fuel mixing prior to combustion leading to more complete combustion and increased engine performance, converter efficiency and converter durability.